ottlukas opened a new issue, #637:
URL: https://github.com/apache/plc4x/issues/637
STRING tag reads in plc4j using eip are not returning the string. The error
returned is:
java.lang.NullPointerException: Cannot invoke
"org.apache.plc4x.java.api.value.PlcValue.getString()" because the return value
of "org.apache.plc4x.java.api.messages.PlcReadResponse.getPlcValue(String)" is
null
It looks like plc4j is considering it a structure or array. If I read with
```
%MyString[{index}]:STRING:1
```
I can get the individual characters in the string by placing the actual
index in \{index}. So it knows where to start reading the data from.
When running a wireshark cap, I can see the returned string in the response
from the PLC. Attached is a pcap of the transaction.
Code Snippet:
```
try (PlcConnection plcConnection = new
PlcDriverManager().getConnection("eip://127.0.0.1")) {
if (!plcConnection.getMetadata().canRead()) {
logger.error("PLC connection doesn't support
reading.");
return;
}
logger.info("PLC connector connected"); // Create a new
read request:
PlcReadRequest.Builder builder = plcConnection.readRequestBuilder();
logger.info("Created
Builder");
builder.addItem("value-1", "%MyString:STRING:1");
PlcReadRequest readRequest =
builder.build(); // Register a callback executed as soon as a response
arrives.
logger.info("Make
sync request for PLC data");
PlcReadResponse readResponse = readRequest.execute().get(5000,
TimeUnit.MILLISECONDS);
if (readResponse != null) {
printPlcResponse(readResponse);
} else {
logger.error("An
error reading PLC, response is NULL");
}
for (String field : readResponse.getFieldNames()){
rtnArray.add(new PlcReadResponseData(field,
readResponse.getPlcValue(field).getString())
); // Exception is thrown here
}
} catch (PlcConnectionException e) {
e.printStackTrace();
}
```
Imported from Jira
[PLC4X-341](https://issues.apache.org/jira/browse/PLC4X-341). Original Jira may
contain additional context.
Reported by: AndyGPLC.
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